U.S. patent application number 11/598354 was filed with the patent office on 2007-05-17 for high q and low stress capacitor electrode array.
Invention is credited to James Martin.
Application Number | 20070109716 11/598354 |
Document ID | / |
Family ID | 40669505 |
Filed Date | 2007-05-17 |
United States Patent
Application |
20070109716 |
Kind Code |
A1 |
Martin; James |
May 17, 2007 |
High Q and low stress capacitor electrode array
Abstract
An embodiment of the present invention provides a capacitor,
comprising a solid electrode, an electrode broken into subsections
with a signal bus lines connecting the subsections; and wherein the
signal bus further connects the solid electrode with the electrode
broken into subsections.
Inventors: |
Martin; James; (Londonderry,
NH) |
Correspondence
Address: |
James S. Finn;C/O William Tucker
14431 Goliad Dr., Box #8
Malakoff
TX
75148
US
|
Family ID: |
40669505 |
Appl. No.: |
11/598354 |
Filed: |
November 13, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60736366 |
Nov 14, 2005 |
|
|
|
Current U.S.
Class: |
361/303 |
Current CPC
Class: |
H01G 7/06 20130101; H01G
4/228 20130101; Y10T 29/435 20150115; H01L 2924/0002 20130101; Y10T
29/43 20150115; H01G 4/38 20130101; H01L 23/5223 20130101; H01L
28/87 20130101; Y10T 29/49005 20150115; H01L 2924/0002 20130101;
H01L 2924/00 20130101 |
Class at
Publication: |
361/303 |
International
Class: |
H01G 4/005 20060101
H01G004/005 |
Claims
1. An apparatus, comprising: a capacitor including a solid
electrode; and an electrode broken into subsections with a signal
bus lines connecting said subsections and said solid electrode.
2. The apparatus of claim 1, wherein said broken electrode
distributes the signal across said capacitor area and increases the
effective width of a signal path through said solid electrode.
3. The apparatus of claim 1, wherein said capacitor is a planar
integrated capacitors as well as discrete ceramic capacitors. This
structure also reduces the mechanical stresses generated in the
metals and dielectric films of the capacitor.
4. The apparatus of claim 1, wherein said capacitor is a discrete
ceramic capacitor.
5. The apparatus of claim 2, wherein said solid electrode and said
broken electrode are adapted to reduce the mechanical stresses
generated in the metals and dielectric films of said capacitor.
6. The apparatus of claim 1, wherein said capacitor is in a pair of
series capacitors and wherein said subsections are arranged in such
a manner that it increases the effective width of the signal path
in said solid electrode.
7. The apparatus of claim 6, wherein said at least one voltage
tunable dielectric capacitor is a series network of voltage tunable
dielectric capacitors which are all tuned using a common tuning
voltage.
8. A method, comprising: breaking an electrode into subsections
with signal bus lines connecting said subsections and a solid
electrode to improve Q.
9. The method of claim 8, further comprising distributing the
signal across said capacitor area by said broken electrode and
thereby increasing the effective width of a signal path through
said solid electrode.
10. The method of claim 8, wherein said capacitor is a planar
integrated capacitors.
11. The method of claim 8, wherein said capacitor is a discrete
ceramic capacitor.
12. The method of claim 9, further comprising adapting said solid
electrode and said broken electrode to reduce the mechanical
stresses generated in the metals and dielectric films of said
capacitor.
13. The method of claim 8, further comprising using said capacitor
in a pair of series capacitors and wherein said subsections are
arranged in such a manner that it increases the effective width of
the signal path in said solid electrode.
14. The method of claim 6, wherein said at least one voltage
tunable dielectric capacitor is a series network of voltage tunable
dielectric capacitors which are all tuned using a common tuning
voltage.
15. A capacitor, comprising: a solid electrode; an electrode broken
into subsections with a signal bus lines connecting said
subsections; and wherein said signal bus further connects said
solid electrode with said electrode broken into subsections.
16. The capacitor of claim 15, further comprising a voltage tunable
dielectric material between said solid electrode and said electrode
broken into subsections to enable said capacitor to be voltage
tunable.
17. The capacitor of claim 15, wherein said broken electrode
distributes the signal across said capacitor area and increases the
effective width of a signal path through said solid electrode.
18. The capacitor of claim 15, wherein said capacitor is a planar
integrated capacitors or a discrete ceramic capacitor.
19. The capacitor of claim 15, wherein said capacitor is in a pair
of series capacitors and wherein said subsections are arranged in
such a manner that it increases the effective width of the signal
path in said solid electrode.
20. The capacitor of claim 19, wherein said at least one voltage
tunable dielectric capacitor is a series network of voltage tunable
dielectric capacitors which are all tuned using a common tuning
voltage.
21. The apparatus of claim 1, wherein said subsections form a
diamond shape.
22. The apparatus of claim 1, wherein said subsections form a
plurality of adjacent rectangular shapes.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application claims the benefit of priority under 35
U.S.C Section 119 from U.S. Provisional Application Ser. No.
60/736,366, filed Nov. 14, 2005, entitled, HIGH Q AND LOW STRESS
CAPACITOR ELECTRODE ARRAY, by James Martin.
BACKGROUND OF THE INVENTION
[0002] One of the most important parameters in evaluating a high
frequency chip capacitor is the Q factor, or the related equivalent
series resistance (ESR). In theory, a "perfect" capacitor would
exhibit an ESR of 0 (zero) ohms and would be purely reactive with
no real (resistive) component. The current going through the
capacitor would lead the voltage across the capacitor by exactly 90
degrees at all frequencies.
[0003] In real world usage, no capacitor is perfect, and will
always exhibit some finite amount of ESR. The ESR varies with
frequency for a given capacitor, and is "equivalent" because its
source is from the characteristics of the conducting electrode
structures and in the insulating dielectric structure. For the
purpose of modeling, the ESR is represented as a single series
parasitic element. In past decades, all capacitor parameters were
measured at a standard of 1 MHz, but in today's high frequency
world, this is far from sufficient. Typical values for a good high
frequency capacitor of a given value could run in the order of
about 0.05 ohms at 200 MHz, 0.11 ohms at 900 MHz, and 0.14 ohms at
2000 MHz.
[0004] The quality factor Q, is a dimensionless number that is
equal to the capacitor's reactance divided by the capacitor's
parasitic resistance (ESR). The value of Q changes greatly with
frequency as both reactance and resistance change with frequency.
The reactance of a capacitor changes tremendously with frequency or
with the capacitance value, and therefore the Q value could vary by
a great amount.
[0005] Since a high capacitor Q is vital to many applications, a
strong industry need exists for the high Q and low stress capacitor
electrode array of the present invention.
SUMMARY OF THE INVENTION
[0006] An embodiment of the present invention provides a capacitor,
comprising a solid electrode, an electrode broken into subsections
with a signal bus lines connecting the subsections; and wherein the
signal bus further connects the solid electrode with the electrode
broken into subsections. The capacitor of an embodiment of the
present invention may further comprise a voltage tunable dielectric
material between the solid electrode and the electrode broken into
subsections to enable the capacitor to be voltage tunable. The
broken electrode may distribute the signal across the capacitor
area and increase the effective width of a signal path through the
solid electrode. In an embodiment of the present invention and not
limited in this respect, the capacitor may be a planar integrated
capacitors or a discrete ceramic capacitor and the capacitor may be
a pair of series capacitors and wherein the subsections are
arranged in such a manner that it increases the effective width of
the signal path in the solid electrode.
BRIEF DESCRIPTION OF THE DRAWINGS
[0007] The present invention is described with reference to the
accompanying drawings. In the drawings, like reference numbers
indicate identical or functionally similar elements. Additionally,
the left-most digit(s) of a reference number identifies the drawing
in which the reference number first appears.
[0008] FIG. 1 illustrates three, of many possible, capacitor
electrode structures of some embodiments of the present invention;
and
[0009] FIG. 2 illustrates a method of one embodiment of the present
invention.
DETAILED DESCRIPTION
[0010] In the following detailed description, numerous specific
details are set forth in order to provide a thorough understanding
of the invention. However, it will be understood by those skilled
in the art that the present invention may be practiced without
these specific details. In other instances, well-known methods,
procedures, components and circuits have not been described in
detail so as not to obscure the present invention.
[0011] Use of the terms "coupled" and "connected", along with their
derivatives, may be used. It should be understood that these terms
are not intended as synonyms for each other. Rather, in particular
embodiments, "connected" may be used to indicate that two or more
elements are in direct physical or electrical contact with each
other. "Coupled" my be used to indicated that two or more elements
are in either direct or indirect (with other intervening elements
between them) physical or electrical contact with each other,
and/or that the two or more elements co-operate or interact with
each other (e.g. as in a cause an effect relationship).
[0012] An embodiment of the present invention provides a capacitor
electrode structure that allows for the creation of very high "Q"
(low resistance) capacitors. It is particularly well suited to
common capacitor material structures wherein one electrode is made
from a higher resistance metal than the opposite electrode.
Examples of capacitors with such material properties can be found
in planar integrated capacitors, as well as discrete ceramic
capacitors. The structure of an embodiment of the present invention
also reduces the mechanical stresses generated in the metals and
dielectric films of the capacitor. The invention includes
electrodes broken into subsections, signal bus lines to connect the
subsections, and a solid electrode. The broken electrode should
have the lower resistance of the two. The broken electrode may
distribute the signal across the capacitor area and, through proper
arrangement, increase the effective width of the signal path
through the higher resistance solid electrode. The signal busses
may bring in and take out the signal. In an embodiment of the
present invention, the present electrodes may include a voltage
tunable dielectric material between the electrodes and the voltage
tunable dielectric material may be a Parascan.RTM. voltage tunable
dielectric material.
[0013] This structure realizes these benefits by breaking two of
the electrodes of a pair of series capacitors into subsections. The
sections are arranged in such a manner that it increases the
effective width of the signal path in the higher resistance
electrode. These subsections are then electrically connected
through a bus. The reduction in stress occurs because the
individual electrode subsections retain and create less stress than
a single plate of similar area.
[0014] Turning now to the figures, in FIG. 1, shown generally as
100 are images of two series capacitors. The left most design 110
is fairly standard with solid high resistance electrode 120 and low
resistance electrodes 122 connected by bus 115. Although not
limited in this respect, two exemplary embodiments of the present
invention are shown in the center 125 and on the right 140. Center
capacitor 125 may include solid high resistance electrode 135 and
low resistance electrodes 132 connected by bus 130. Right capacitor
140 may include solid high resistance electrode 150 and low
resistance electrodes 155 connected by bus 145. The reduction in
resistance, leading to an increase in Q, occurs because the length
of the signal path stays the same while the effective width
increases. For example, breaking the electrode as shown in the
middle image 125 increases the width to 3.5 times that of the
conventional capacitor. The rightmost "diamond" configuration 140
increases that width to 4.25 times that of the conventional.
[0015] Turning now to FIG. 2, generally at 200, is provided a
method according to one embodiment of the present invention which
may comprise breaking an electrode into subsections 205 with signal
bus lines connecting said subsections 210 and a solid electrode 215
to improve Q. The method may further comprise distributing the
signal across said capacitor area by said broken electrode and
thereby increasing the effective width of a signal path through
said solid electrode. The capacitor may be a planar integrated
capacitor or a discrete ceramic capacitor in the method of an
embodiment of the present invention. The method may still further
comprise adapting said solid electrode and said broken electrode to
reduce the mechanical stresses generated in the metals and
dielectric films of said capacitor and as shown at 220 using said
capacitor in a pair of series capacitors and wherein said
subsections are arranged in such a manner that it increases the
effective width of the signal path in said solid electrode. In an
embodiment of the present method the at least one voltage tunable
dielectric capacitor may be a series network of voltage tunable
dielectric capacitors which are all tuned using a common tuning
voltage.
[0016] Throughout the aforementioned description, BST may be used
as a tunable dielectric material that may be used in a tunable
dielectric capacitor of the present invention. However, the
assignee of the present invention, Paratek Microwave, Inc. has
developed and continues to develop tunable dielectric materials
that may be utilized in embodiments of the present invention and
thus the present invention is not limited to using BST material.
This family of tunable dielectric materials may be referred to as
Parascan.RTM..
[0017] The term Parascan.RTM. as used herein is a trademarked term
indicating a tunable dielectric material developed by the assignee
of the present invention. Parascan.RTM. tunable dielectric
materials have been described in several patents. Barium strontium
titanate (BaTiO3-SrTiO3), also referred to as BSTO, is used for its
high dielectric constant (200-6,000) and large change in dielectric
constant with applied voltage (25-75 percent with a field of 2
Volts/micron). Tunable dielectric materials including barium
strontium titanate are disclosed in U.S. Pat. No. 5,312,790 to
Sengupta, et al. entitled "Ceramic Ferroelectric Material"; U.S.
Pat. No. 5,427,988 by Sengupta, et al. entitled "Ceramic
Ferroelectric Composite Material-BSTO-MgO"; U.S. Pat. No. 5,486,491
to Sengupta, et al. entitled "Ceramic Ferroelectric Composite
Material-BSTO-ZrO2"; U.S. Pat. No. 5,635,434 by Sengupta, et al.
entitled "Ceramic Ferroelectric Composite Material-BSTO-Magnesium
Based Compound"; U.S. Pat. No. 5,830,591 by Sengupta, et al.
entitled "Multilayered Ferroelectric Composite Waveguides"; U.S.
Pat. No. 5,846,893 by Sengupta, et al. entitled "Thin Film
Ferroelectric Composites and Method of Making"; U.S. Pat. No.
5,766,697 by Sengupta, et al. entitled "Method of Making Thin Film
Composites"; U.S. Pat. No. 5,693,429 by Sengupta, et al. entitled
"Electronically Graded Multilayer Ferroelectric Composites"; U.S.
Pat. No. 5,635,433 by Sengupta entitled "Ceramic Ferroelectric
Composite Material BSTO-ZnO"; U.S. Pat. No. 6,074,971 by Chiu et
al. entitled "Ceramic Ferroelectric Composite Materials with
Enhanced Electronic Properties BSTO Mg Based Compound-Rare Earth
Oxide". These patents are incorporated herein by reference. The
materials shown in these patents, especially BSTO-MgO composites,
show low dielectric loss and high tunability. Tunability is defined
as the fractional change in the dielectric constant with applied
voltage.
[0018] Barium strontium titanate of the formula
Ba.sub.xSr.sub.1-xTiO.sub.3 is a preferred electronically tunable
dielectric material due to its favorable tuning characteristics,
low Curie temperatures and low microwave loss properties. In the
formula Ba.sub.xSr.sub.1-xTiO.sub.3, x can be any value from 0 to
1, preferably from about 0.15 to about 0.6. More preferably, x is
from 0.3 to 0.6.
[0019] Other electronically tunable dielectric materials may be
used partially or entirely in place of barium strontium titanate.
An example is Ba.sub.xCa.sub.1-xTiO.sub.3, where x is in a range
from about 0.2 to about 0.8, preferably from about 0.4 to about
0.6. Additional electronically tunable ferroelectrics include
Pb.sub.xZr.sub.1-xTiO.sub.3 (PZT) where x ranges from about 0.0 to
about 1.0, Pb.sub.xZr.sub.1-xSrTiO.sub.3 where x ranges from about
0.05 to about 0.4, KTa.sub.xNb.sub.1-xO.sub.3 where x ranges from
about 0.0 to about 1.0, lead lanthanum zirconium titanate (PLZT),
PbTiO.sub.3, BaCaZrTiO.sub.3, NaNO.sub.3, KNbO.sub.3, LiNbO.sub.3,
LiTaO.sub.3, PbNb.sub.2O.sub.6, PbTa.sub.2O.sub.6, KSr(NbO.sub.3)
and NaBa.sub.2(NbO.sub.3)5KH.sub.2PO.sub.4, and mixtures and
compositions thereof. Also, these materials can be combined with
low loss dielectric materials, such as magnesium oxide (MgO),
aluminum oxide (Al.sub.2O.sub.3), and zirconium oxide (ZrO.sub.2),
and/or with additional doping elements, such as manganese (MN),
iron (Fe), and tungsten (W), or with other alkali earth metal
oxides (i.e. calcium oxide, etc.), transition metal oxides,
silicates, niobates, tantalates, aluminates, zirconnates, and
titanates to further reduce the dielectric loss.
[0020] In addition, the following U.S. patents and patent
Applications, assigned to the assignee of this application,
disclose additional examples of tunable dielectric materials: U.S.
Pat. No. 6,514,895, entitled "Electronically Tunable Ceramic
Materials Including Tunable Dielectric and Metal Silicate Phases";
U.S. Pat. No. 6,774,077, entitled "Electronically Tunable, Low-Loss
Ceramic Materials Including a Tunable Dielectric Phase and Multiple
Metal Oxide Phases"; U.S. Pat. No. 6,737,179 filed Jun. 15, 2001,
entitled "Electronically Tunable Dielectric Composite Thick Films
And Methods Of Making Same; U.S. Pat. No. 6,617,062 entitled
"Strain-Relieved Tunable Dielectric Thin Films"; U.S. Pat. No.
6,905,989, filed May 31, 2002 entitled "Tunable Dielectric
Compositions Including Low Loss Glass"; U.S. patent application
Ser. No. 10/991,924, filed Nov. 18, 2004 entitled "Tunable Low Loss
Material Compositions and Methods of Manufacture and Use Therefore"
These patents and patent applications are incorporated herein by
reference.
[0021] The tunable dielectric materials can also be combined with
one or more non-tunable dielectric materials. The non-tunable
phase(s) may include MgO, MgAl.sub.2O.sub.4, MgTiO.sub.3,
Mg.sub.2SiO.sub.4, CaSiO.sub.3, MgSrZrTiO.sub.6, CaTiO.sub.3,
Al.sub.2O.sub.3, SiO.sub.2 and/or other metal silicates such as
BaSiO.sub.3 and SrSiO.sub.3. The non-tunable dielectric phases may
be any combination of the above, e.g., MgO combined with
MgTiO.sub.3, MgO combined with MgSrZrTiO.sub.6, MgO combined with
Mg.sub.2SiO.sub.4, MgO combined with Mg.sub.2SiO.sub.4,
Mg.sub.2SiO.sub.4 combined with CaTiO.sub.3 and the like.
[0022] Additional minor additives in amounts of from about 0.1 to
about 5 weight percent can be added to the composites to
additionally improve the electronic properties of the films. These
minor additives include oxides such as zirconnates, tannates, rare
earths, niobates and tantalates. For example, the minor additives
may include CaZrO.sub.3, BaZrO.sub.3, SrZrO.sub.3, BaSnO.sub.3,
CaSnO.sub.3, MgSnO.sub.3, Bi2O.sub.3/2SnO.sub.2, Nd.sub.2O.sub.3,
Pr.sub.7O.sub.11, Yb.sub.2O.sub.3, H.sub.o2O.sub.3,
La.sub.2O.sub.3, MgNb.sub.2O.sub.6, SrNb.sub.2O.sub.6,
BaNb.sub.2O.sub.6, MgTa.sub.2O.sub.6, BaTa.sub.2O.sub.6 and
Ta.sub.2O.sub.3.
[0023] Films of tunable dielectric composites may comprise
Ba1-xSrxTiO3, where x is from 0.3 to 0.7 in combination with at
least one non-tunable dielectric phase selected from MgO,
MgTiO.sub.3, MgZrO.sub.3, MgSrZrTiO.sub.6, Mg.sub.2SiO.sub.4,
CaSiO.sub.3, MgAl.sub.2O.sub.4, CaTiO.sub.3, Al.sub.2O.sub.3,
SiO.sub.2, BaSiO.sub.3 and SrSiO.sub.3. These compositions can be
BSTO and one of these components, or two or more of these
components in quantities from 0.25 weight percent to 80 weight
percent with BSTO weight ratios of 99.75 weight percent to 20
weight percent.
[0024] The electronically tunable materials may also include at
least one metal silicate phase. The metal silicates may include
metals from Group 2A of the Periodic Table, i.e., Be, Mg, Ca, Sr,
Ba and Ra, preferably Mg, Ca, Sr and Ba. Preferred metal silicates
include Mg.sub.2SiO.sub.4, CaSiO.sub.3, BaSiO.sub.3 and
SrSiO.sub.3. In addition to Group 2A metals, the present metal
silicates may include metals from Group 1A, i.e., Li, Na, K, Rb, Cs
and Fr, preferably Li, Na and K. For example, such metal silicates
may include sodium silicates such as Na.sub.2SiO.sub.3 and
NaSiO.sub.3-5H.sub.2O, and lithium-containing silicates such as
LiAlSiO.sub.4, Li2SiO.sub.3 and Li.sub.4SiO.sub.4. Metals from
Groups 3A, 4A and some transition metals of the Periodic Table may
also be suitable constituents of the metal silicate phase.
Additional metal silicates may include Al.sub.2Si.sub.2O.sub.7,
ZrSiO.sub.4, Ka1Si.sub.3O.sub.8, NaAlSi.sub.3O.sub.8,
CaAl.sub.2Si.sub.2O.sub.8, CaMgSi.sub.2O.sub.6, BaTiSi.sub.3O.sub.9
and Zn.sub.2SiO.sub.4. The above tunable materials can be tuned at
room temperature by controlling an electric field that is applied
across the materials.
[0025] In addition to the electronically tunable dielectric phase,
the electronically tunable materials can include at least two
additional metal oxide phases. The additional metal oxides may
include metals from Group 2A of the Periodic Table, i.e., Mg, Ca,
Sr, Ba, Be and Ra, preferably Mg, Ca, Sr and Ba. The additional
metal oxides may also include metals from Group 1A, i.e., Li, Na,
K, Rb, Cs and Fr, preferably Li, Na and K. Metals from other Groups
of the Periodic Table may also be suitable constituents of the
metal oxide phases. For example, refractory metals such as Ti, V,
Cr, Mn, Zr, Nb, Mo, Hf, Ta and W may be used. Furthermore, metals
such as Al, Si, Sn, Pb and Bi may be used. In addition, the metal
oxide phases may comprise rare earth metals such as Sc, Y, La, Ce,
Pr, Nd and the like.
[0026] The additional metal oxides may include, for example,
zirconnates, silicates, titanates, aluminates, stannates, niobates,
tantalates and rare earth oxides. Preferred additional metal oxides
include Mg.sub.2SiO.sub.4, MgO, CaTiO.sub.3, MgZrSrTiO.sub.6,
MgTiO.sub.3, MgA.sub.12O.sub.4, WO3, SnTiO.sub.4, ZrTiO.sub.4,
CaSiO.sub.3, CaSnO.sub.3, CaWO.sub.4, CaZrO.sub.3,
MgTa.sub.2O.sub.6, MgZrO.sub.3, MnO.sub.2, PbO, Bi.sub.2O.sub.3 and
LaO.sub.3. Particularly preferred additional metal oxides include
Mg.sub.2SiO.sub.4, MgO, CaTiO.sub.3, MgZrSrTiO.sub.6, MgTiO.sub.3,
MgAl.sub.2O.sub.4, MgTa.sub.2O.sub.6 and MgZrO.sub.3.
[0027] The additional metal oxide phases are typically present in
total amounts of from about 1 to about 80 weight percent of the
material, preferably from about 3 to about 65 weight percent, and
more preferably from about 5 to about 60 weight percent. In one
preferred embodiment, the additional metal oxides comprise from
about 10 to about 50 total weight percent of the material. The
individual amount of each additional metal oxide may be adjusted to
provide the desired properties. Where two additional metal oxides
are used, their weight ratios may vary, for example, from about
1:100 to about 100:1, typically from about 1:10 to about 10:1 or
from about 1:5 to about 5:1. Although metal oxides in total amounts
of from 1 to 80 weight percent are typically used, smaller additive
amounts of from 0.01 to 1 weight percent may be used for some
applications.
[0028] The additional metal oxide phases can include at least two
Mg-containing compounds. In addition to the multiple Mg-containing
compounds, the material may optionally include Mg-free compounds,
for example, oxides of metals selected from Si, Ca, Zr, Ti, Al
and/or rare earths.
[0029] While the present invention has been described in terms of
what are at present believed to be its preferred embodiments, those
skilled in the art will recognize that various modifications to the
disclose embodiments can be made without departing from the scope
of the invention as defined by the following claims.
* * * * *